Diet and Microbiome-directed therapy 2.0 for IBD.

Inflammatory bowel disease (IBD) are chronic and relapsing disorders of the gastrointestinal tract, characterized by dysregulated immune responses to the gut microbiome. The gut microbiome and diet are key environmental factors that influence the onset and progression of IBD and can be leveraged for treatment. In this review, we summarize the current evidence on the role of the gut microbiome and diet in IBD pathogenesis, and the potential of microbiome-directed therapies and dietary interventions and improve IBD outcomes. We discuss available data, the advantages and drawbacks of the different approaches to manipulate the gut microbiome, such as fecal microbiota transplantation, next-generation and conventional probiotics, and postbiotics. We also review the use of diet as a therapeutic tool in IBD, including the effects in induction and maintenance, special diets, and exclusive enteral nutrition. Finally, we highlight the challenges and opportunities for the translation of diet and microbiome interventions into clinical practice, such as the need for personalization, manufacturing and regulatory hurdles, and the specificity to take into account for clinical trial design.

Contextual AI models for single-cell protein biology.

Understanding protein function and developing molecular therapies require deciphering the cell types in which proteins act as well as the interactions between proteins. However, modeling protein interactions across biological contexts remains challenging for existing algorithms. Here we introduce PINNACLE, a geometric deep learning approach that generates context-aware protein representations. Leveraging a multiorgan single-cell atlas, PINNACLE learns on contextualized protein interaction networks to produce 394,760 protein representations from 156 cell type contexts across 24 tissues. PINNACLE's embedding space reflects cellular and tissue organization, enabling zero-shot retrieval of the tissue hierarchy. Pretrained protein representations can be adapted for downstream tasks: enhancing 3D structure-based representations for resolving immuno-oncological protein interactions, and investigating drugs' effects across cell types. PINNACLE outperforms state-of-the-art models in nominating therapeutic targets for rheumatoid arthritis and inflammatory bowel diseases and pinpoints cell type contexts with higher predictive capability than context-free models. PINNACLE's ability to adjust its outputs on the basis of the context in which it operates paves the way for large-scale context-specific predictions in biology.

Periodontitis is an immune-related adverse event associated with immune checkpoint inhibitors: A multi-center cohort study.

Immune checkpoint inhibitors (ICIs) cause immune-related adverse events (irAEs) across various organ systems including oral health complications such as dry mouth and stomatitis. In this study, we aimed to determine the risk of periodontitis among patients on immune checkpoint inhibitors (ICIs) and to test the associations between ICI-associated periodontitis and other immune-related adverse events (irAEs). We performed a retrospective cohort study involving adult cancer patients between January 2010 and November 2021. Patients on an ICI were propensity score-matched to patients not on an ICI. The primary outcome was the occurrence of periodontitis. ICIs included programmed cell death 1 (PD-1) inhibitors programmed cell death ligand 1 (PD-L1) inhibitors, and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors. The risk of periodontitis following ICI use was derived through a Cox proportional hazard model and Kaplan-Meier survival analysis. Overall, 868 patients on an ICI were matched to patients not on an ICI. Among the ICI cohort, 41 (4.7 %) patients developed periodontitis. The incidence rate of periodontitis was significantly higher in patients on an ICI than in patients not on an ICI (55.3 vs 25.8 per 100 patient-years, incidence rate ratio = 2.14, 95 % CI = 1.38-3.33). Both the use of PD-L1 inhibitors (multivariate HR = 2.5, 95%CI = 1.3-4.7) and PD-1 inhibitors (multivariate HR = 2.0, 95%CI = 1.2-3.2) were associated with the risk of periodontitis. The presence of immune-related periodontitis was associated with better overall survival (not reached vs 17 months, log-rank p-value<0.001), progression-free survival (14.9 vs 5.6 months, log-rank p-value = 0.01), and other concomitant immune-related cutaneous adverse events. In conclusion, ICI was associated with an increased risk of periodontitis. Immune-related periodontitis as an irAE was associated with better cancer survival and concomitant cutaneous irAEs.

IBD Is Like a Tree: Reflections From Older Adults With Inflammatory Bowel Disease.

BACKGROUND: Despite the growing proportion of older adults with inflammatory bowel disease (IBD), their lived experience is not well understood. IBD literature is generally focused on younger adults, and few studies are qualitative. Older adults may report well-being differently than younger adults, so it is important that we learn about their goals and priorities with a chronic disease. OBJECTIVE: The study sought to understand the lived experience of older adults with IBD and explore their perceptions and priorities. METHODS: We conducted in-depth interviews with patients ≥60 years of age with IBD to evaluate the impact and perception of IBD in the context their overall health and life. We used a hybrid inductive-deductive thematic analysis of our transcripts to identify underlying patterns. RESULTS: We achieved thematic saturation after 22 interviews. We produced 4 major themes: (1) having IBD at an older age, (2) financial ramifications of IBD at an older age, (3) expectations for a meaningful life, and (4) unmet needs. Prominent subthemes included (1) ageism, loss of autonomy, and barriers to healthcare; (2) retirement and insurance issues; (3) redefining quality of life and gratitude; and (4) social isolation and navigating daily life with IBD. CONCLUSIONS: Having IBD later in life presents unique challenges. Physicians treating older patients should consider age-sensitive communication, susceptibility to social isolation, and practices for healthy aging in the context of IBD. Patient priorities for further investigation include more representation in the media and educational material tailored for older adults with IBD.

In this qualitative study, we employ in-depth interviews to report the lived experience of older adults with inflammatory bowel disease and explore their perceptions and priorities of living with this chronic disease.

Diagnosis of Inflammatory Bowel Disease-Associated Peripheral Arthritis: A Systematic Review.

BACKGROUND: Inflammatory bowel disease (IBD)-associated peripheral spondyloarthritis (pSpA) decreases quality of life and remains poorly understood. Given the prevalence of this condition and its negative impact, it is surprising that evidence-based disease definitions and diagnostic strategies are lacking. This systematic review summarizes available data to facilitate development and validation of diagnostics, patient-reported outcomes, and imaging indices specific to this condition. METHODS: A literature search was conducted. Consensus or classification criteria, case series, cross-sectional studies, cohort studies, and randomized controlled trials related to diagnosis were included. RESULTS: A total of 44 studies reporting data on approximately 1500 patients with pSpA were eligible for analysis. Data quality across studies was only graded as fair to good. Due to large heterogeneity, meta-analysis was not possible. The majority of studies incorporated patient-reported outcomes and a physical examination. A total of 13 studies proposed or validated screening tools, consensus, classification, or consensus criteria. A total of 28 studies assessed the role of laboratory tests, none of which were considered sufficiently accurate for use in diagnosis. A total of 17 studies assessed the role of imaging, with the available literature insufficient to fully endorse any imaging modality as a robust diagnostic tool. CONCLUSIONS: This review highlights existing inconsistency and lack of a clear diagnostic approach for IBD-associated pSpA. Given the absence of an evidence-based approach, a combination of existing criteria and physician assessment should be utilized. To address this issue comprehensively, our future efforts will be directed toward pursuit of a multidisciplinary approach aimed at standardizing evaluation and diagnosis of IBD-associated pSpA.

This systematic review highlights the lack of an evidence-based approach to the diagnosis of inflammatory bowel disease­associated peripheral spondyloarthritis and the need to standardize evaluation and diagnosis via multidisciplinary collaboration with development of patient-reported outcomes and imaging indices.

Discovery of disease-adapted bacterial lineages in inflammatory bowel diseases.

Gut bacteria are implicated in inflammatory bowel disease (IBD), but the strains driving these associations are unknown. Large-scale studies of microbiome evolution could reveal the imprint of disease on gut bacteria, thus pinpointing the strains and genes that may underlie inflammation. Here, we use stool metagenomes of thousands of IBD patients and healthy controls to reconstruct 140,000 strain genotypes, revealing hundreds of lineages enriched in IBD. We demonstrate that these strains are ancient, taxonomically diverse, and ubiquitous in humans. Moreover, disease-associated strains outcompete their healthy counterparts during inflammation, implying long-term adaptation to disease. Strain genetic differences map onto known axes of inflammation, including oxidative stress, nutrient biosynthesis, and immune evasion. Lastly, the loss of health-associated strains of Eggerthella lenta was predictive of fecal calprotectin, a biomarker of disease severity. Our work identifies reservoirs of strain diversity that may impact inflammatory disease and can be extended to other microbiome-associated diseases.

Challenges in IBD Research 2024: Environmental Triggers.

Environmental factors play an important role in inflammatory bowel diseases (IBD; Crohn's disease, [CD], ulcerative colitis [UC]). As part of the Crohn's & Colitis Challenges 2024 agenda, the Environmental Triggers workgroup summarized the progress made in the field of environmental impact on IBD since the last Challenges cycle in this document. The workgroup identified 4 unmet gaps in this content area pertaining to 4 broad categories: (1) Epidemiology; (2) Exposomics and environmental measurement; (3) Biologic mechanisms; and (4) Interventions and Implementation. Within epidemiology, the biggest unmet gaps were in the study of environmental factors in understudied populations including racial and ethnic minority groups and in populations witnessing rapid rise in disease incidence globally. The workgroup also identified a lack of robust knowledge of how environmental factors may impact difference stages of the disease and for different disease-related end points. Leveraging existing cohorts and targeted new prospective studies were felt to be an important need for the field. The workgroup identified the limitations of traditional questionnaire-based assessment of environmental exposure and placed high priority on the identification of measurable biomarkers that can quantify cross-sectional and longitudinal environmental exposure. This would, in turn, allow for identifying the biologic mechanisms of influence of environmental factors on IBD and understand the heterogeneity in effect of such influences. Finally, the working group emphasized the importance of generating high-quality data on effective environmental modification on an individual and societal level, and the importance of scalable and sustainable methods to deliver such changes.

Environmental factors are important in inflammatory bowel diseases. It is a high priority to identify environmental factors impacting different disease stages and in different populations, develop biomarkers for such exposures, and generate evidence for modifying them to improve outcomes.

Physical Activity Is Associated With A Decreased Risk Of Developing Inflammatory Bowel Disease: A Systematic Review And Meta-Analysis.

BACKGROUND AND AIMS: Modifiable risk factors in Inflammatory Bowel Disease (IBD), such as physical activity, may be utilised as prevention strategies. However, the findings of previous studies on the association between physical activity and IBD risk have been inconsistent. We aimed to perform a systematic review and meta-analysis to estimate the effect of physical activity on IBD risk. METHODS: A search was conducted for relevant studies published before April 2023 that assessed the effect of pre-IBD diagnosis levels of physical activity on IBD incidence. Individual summary statistics (relative risks; RR), and confidence intervals (CI) were extracted with forest plots generated. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence. RESULTS: 10 observational studies were included. For cohort studies, there were 1,182 Crohn's disease (CD) and 2,361 ulcerative colitis (UC) patients, with 860,992 participants without IBD. For case-control studies, there were 781 CD to 2,636 controls, and 1,127 UC to 3,752 controls. Compared to individuals with low physical activity levels, the RRs of CD in individuals with high physical activity levels for cohort and case-control studies were 0.78 (95% CI 0.68-0.88, P = 0.0001) and 0.87 (95% CI 0.79-0.95, P = 0.003), respectively. For UC, the RRs were 0.62 (95% CI 0.43-0.88, P = 0.008) and 0.74 (95% CI 0.51-1.07, P = 0.11). CONCLUSION: This meta-analysis suggests that physical activity is inversely associated with the risk of developing IBD, more so in CD than in UC.

Comprehensive Association Analyses of Extraintestinal Manifestations in Inflammatory Bowel Disease.

BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) frequently develop extraintestinal manifestations (EIMs) that contribute substantially to morbidity. We assembled the largest multicohort data set to date to investigate the clinical, serologic, and genetic factors associated with EIM complications in IBD. METHODS: Data were available in 12,083 unrelated European ancestry IBD cases with presence or absence of EIMs (eg, ankylosing spondylitis [ankylosing spondylitis and sacroiliitis], primary sclerosing cholangitis [PSC], peripheral arthritis, and skin and ocular manifestations) across 4 cohorts (Cedars-Sinai Medical Center, National Institute for Diabetes and Digestive and Kidney Diseases IBD Genetics Consortium, Sinai Helmsley Alliance for Research Excellence Consortium, and Risk Stratification and Identification of Immunogenetic and Microbial Markers of Rapid Disease Progression in Children with Crohn's Disease cohort). Clinical and serologic parameters were analyzed by means of univariable and multivariable regression analyses using a mixed-effects model. Within-case logistic regression was performed to assess genetic associations. RESULTS: Most EIMs occurred more commonly in female subjects (overall EIM: P = 9.0E-05, odds ratio [OR], 1.2; 95% CI, 1.1-1.4), with CD (especially colonic disease location; P = 9.8E-09, OR, 1.7; 95% CI, 1.4-2.0), and in subjects who required surgery (both CD and UC; P = 3.6E-19, OR, 1.7; 95% CI, 1.5-1.9). Smoking increased risk of EIMs except for PSC, where there was a "protective" effect. Multiple serologic associations were observed, including with PSC (anti-nuclear cytoplasmic antibody; IgG and IgA, anti-Saccharomyces cerevisiae antibodies; and anti-flagellin) and any EIM (anti-nuclear cytoplasmic antibody; IgG and IgA, anti-Saccharomyces cerevisiae antibodies; and anti-Pseudomonas fluorescens-associated sequence). We identified genome-wide significant associations within major histocompatibility complex (ankylosing spondylitis and sacroiliitis, P = 1.4E-15; OR, 2.5; 95% CI, 2.0-3.1; PSC, P = 2.7E-10; OR, 2.8; 95% CI, 2.0-3.8; ocular, P = 2E-08, OR, 3.6; 95% CI, 2.3-5.6; and overall EIM, P = 8.4E-09; OR, 2.2; 95% CI, 1.7-2.9) and CPEB4 (skin, P = 2.7E-08; OR, 1.5; 95% CI, 1.3-1.8). Genetic associations implicated tumor necrosis factor, JAK-STAT, and IL6 as potential targets for EIMs. Contrary to previous reports, only 2% of our subjects had multiple EIMs and most co-occurrences were negatively correlated. CONCLUSIONS: We have identified demographic, clinical, and genetic associations with EIMs that revealed underlying mechanisms and implicated novel and existing drug targets-important steps toward a more personalized approach to IBD management.

Meta-analysis: Risk of pancreatic cancer in patients with inflammatory bowel disease.

BACKGROUND: Studies exploring the association between inflammatory bowel disease (IBD) and pancreatic cancer have reported inconsistent results. AIMS: To provide a comprehensive overview of the risk of pancreatic cancer development in patients with IBD. METHODS: We searched Embase, PubMed, Scopus and ProQuest from inception to 31 October 2023. We included population-based cohort studies examining the risk of incident pancreatic cancer in adult patients with IBD compared to the non-IBD population. We also retrieved Mendelian randomisation (MR) studies investigating the relationship of IBD with pancreatic cancer risk. We conducted random-effects meta-analyses and provided pooled relative risks (RRs) with 95% confidence intervals (CIs). RESULTS: We included 13 studies. Among 11 cohort studies, the risk of developing pancreatic cancer increased by 79% in patients with IBD (RR = 1.79 [95% CI: 1.16-2.75]; I2 = 95.7%). Patients either with Crohn's disease (RR = 1.42 [95% CI: 1.24-1.63]) or ulcerative colitis (RR = 1.50 [95% CI: 1.17-1.92]) had increased risk (p for interaction = 0.72). The annual incidence of pancreatic cancer potentially attributable to IBD increased by 55 cases (95% CI: 17-103) per million. Two MR studies demonstrated that genetic liability to IBD was associated with an increased risk of pancreatic cancer. CONCLUSIONS: Our results suggest a moderate increase in the risk of pancreatic cancer in patients with IBD, which may be further heightened by genetic predisposition to IBD. The increased risk of pancreatic cancer is probably similar in Crohn's disease and ulcerative colitis.

Risk of Common Neurological Disorders in Adult Patients with Inflammatory Bowel Disease: A Systematic Review and Meta-analysis.

BACKGROUND: Several studies investigated the risks of neurological conditions in patients with inflammatory bowel disease (IBD), with some variability in findings. We aimed to perform a systematic review and meta-analysis of available evidence to elucidate the association between IBD and the risks of common neurological disorders. METHODS: We conducted a literature search through Embase, PubMed, Scopus, and ProQuest databases from inception to June 30, 2023, to identify cohort studies assessing the risk of developing stroke, all-cause dementia, Parkinson's disease (PD), multiple sclerosis (MS), seizure/epilepsy, and peripheral neuropathy in adult IBD patients compared with non-IBD population. We combined hazard ratios (HRs) with 95% confidence intervals (CIs) to compute pooled estimates using a random-effects model. RESULTS: In total, 22 cohort studies were included, of which 9 studies reported 7074 stroke events in 202 460 IBD patients, 5 studies reported 3783 all-cause dementia diagnoses in 109 602 IBD patients, 7 studies reported 932 PD diagnoses in 354 792 IBD patients, and 1 study reported 6 MS events in 35 581 IBD patients. We observed increased risks of incident stroke (pooled HR = 1.19; 95% CI, 1.06-1.31), all-cause dementia (pooled HR = 1.22; 95% CI, 1.05-1.38), PD (pooled HR = 1.39; 95% CI, 1.20-1.58), and MS (HR = 2.89; 95% CI, 1.02-8.42). No eligible studies were found on peripheral neuropathy and seizure/epilepsy. CONCLUSIONS: Inflammatory bowel disease may be modestly associated with increased risks of stroke, all-cause dementia, and PD. Further longitudinal studies are warranted to investigate potential links with MS, seizure/epilepsy, and peripheral neuropathy, as well as their clinical significance.

This systematic review and meta-analysis of cohort studies aimed to clarify association between inflammatory bowel disease and risks of common neurological disorders. Based on analyses, inflammatory bowel disease may modestly increase risks of stroke, all-cause dementia, and Parkinson's disease vs the healthy population.

Prevalence and Appropriateness of Polypharmacy in Older Adults with Inflammatory Bowel Diseases.

BACKGROUND: Despite the growing prevalence of older adults with inflammatory bowel diseases (IBD), polypharmacy, an important geriatric construct, is poorly understood. We described polypharmacy and its implications in older adults with IBD. METHODS: In a cross sectional study of adults ≥ 60 years with IBD, we obtained medication lists from the medical record and patients. We assessed medications by the Beer's criteria, anti-cholinergic burden and drug-drug interactions. We constructed multi-variate logistic regression models to assess association between polypharmacy with low quality-of-life, controlling for age, sex, IBD-type, number of comorbidities and depression. RESULTS: In 100 adults ≥ 60 years with IBD, with a median age of 68 years, 56% met criteria for remission by a validated disease activity index. Polypharmacy, defined as ≥ 5 concomitant medications, was noted in 86% of the cohort and 45% had severe polypharmacy, defined as ≥ 10 concomitant medications. In this cohort, 48% were on ≥ 1 medication that met Beer's criteria for potentially inappropriate in older adults and 24% had a cumulative anti-cholinergic drug burden score of ≥ 3, the threshold for serious adverse events attributed to anti-cholinergic burden. Serious drug-drug interactions were found in 26% with 7% involving an IBD medication. Controlling for potential confounders, polypharmacy, defined both numerically (OR 22.79, p < 0.01) and by medication appropriateness (OR 1.95, p < 0.01), was significantly associated with low quality of life. CONCLUSION: Polypharmacy is prevalent in older adults with IBD and independently associated with low quality of life. Describing polypharmacy can guide de-prescription strategies tailored to GI clinic for older adults with IBD.

Contextualizing protein representations using deep learning on protein networks and single-cell data.

Understanding protein function and developing molecular therapies require deciphering the cell types in which proteins act as well as the interactions between proteins. However, modeling protein interactions across diverse biological contexts, such as tissues and cell types, remains a significant challenge for existing algorithms. We introduce Pinnacle, a flexible geometric deep learning approach that is trained on contextualized protein interaction networks to generate context-aware protein representations. Leveraging a human multi-organ single-cell transcriptomic atlas, Pinnacle provides 394,760 protein representations split across 156 cell type contexts from 24 tissues and organs. Pinnacle's contextualized representations of proteins reflect cellular and tissue organization and Pinnacle's tissue representations enable zero-shot retrieval of the tissue hierarchy. Pretrained Pinnacle's protein representations can be adapted for downstream tasks: to enhance 3D structure-based protein representations for important protein interactions in immuno-oncology (PD-1/PD-L1 and B7-1/CTLA-4) and to study the effects of drugs across cell type contexts. Pinnacle outperforms state-of-the-art, yet context-free, models in nominating therapeutic targets for rheumatoid arthritis and inflammatory bowel diseases, and can pinpoint cell type contexts that predict therapeutic targets better than context-free models (29 out of 156 cell types in rheumatoid arthritis; 13 out of 152 cell types in inflammatory bowel diseases). Pinnacle is a graph-based contextual AI model that dynamically adjusts its outputs based on biological contexts in which it operates.

Risk of Cancer Recurrence in Patients With Immune-Mediated Diseases With Use of Immunosuppressive Therapies: An Updated Systematic Review and Meta-Analysis.

BACKGROUND & AIMS: There are limited data on the safety of immunosuppressive therapy use in individuals with immune-mediated diseases with a history of malignancy, particularly with newer biologic and small-molecule treatments. METHODS: We performed a systematic search of PubMed and Embase databases to identify studies examining the impact of immunosuppressive therapies on cancer recurrence across several immune-mediated diseases. Studies were pooled together using random-effects meta-analysis and stratified by type of treatment. Primary outcome was occurrence of incident cancers, defined as new or recurrent. RESULTS: Our meta-analysis included 31 studies (17 inflammatory bowel disease, 14 rheumatoid arthritis, 2 psoriasis, and 1 ankylosing spondylitis) contributing 24,328 persons and 85,784 person-years (p-y) of follow-up evaluation. Rates of cancer recurrence were similar among individuals not on immunosuppression (IS) (1627 incident cancers, 43,765 p-y; 35 per 1000 p-y; 95% CI, 27-43), receiving an anti-tumor necrosis factor (571 incident cancers, 17,772 p-y; 32 per 1000 p-y; 95% CI, 25-38), immunomodulators (1104 incident cancers, 17,018 p-y; 46 per 1000 p-y; 95% CI, 31-61), combination immunosuppression (179 incident cancers, 2659 p-y; 56 per 1000 p-y; 95% CI, 31-81). Patients receiving ustekinumab (5 incident cancers, 213 p-y; 21 per 1000 p-y; 95% CI, 0-44) and vedolizumab (37 incident cancers, 1951 p-y; 16 per 1000 p-y; 95% CI, 5-26) had numerically lower rates of cancer. There were no studies on Janus kinase inhibitors. Stratification of studies by timing of immunosuppression initiation did not reveal a medication effect based on early (<5 years) or delayed treatment initiation. CONCLUSIONS: In patients with immune-mediated diseases and a history of malignancy, we observed similar rates of cancer recurrence in those on no immunosuppression compared with different immunosuppressive treatments.

Geographic Inequities in Access to Phase 3 Clinical Trials for Inflammatory Bowel Disease in the United States.

Randomized controlled trials (RCTs) are an important mode of access to treatments for patients with inflammatory bowel diseases (IBDs) (eg, Crohn's disease [CD], ulcerative colitis [UC]), and a critical step in the regulatory process toward the approval of new therapies. Prior studies examining disparities in RCT participation for patients with IBD have importantly focused on racial and age-related disparities.1,2 Lack of geographic access to trials may be an important barrier to participation and a source of inequity. The aim of our study was to geographically map access to phase 3 clinical trials in IBD within the United States, and identify the impact of rural residence and socioeconomic status on access to trials.

Reverse metabolomics for the discovery of chemical structures from humans.

Determining the structure and phenotypic context of molecules detected in untargeted metabolomics experiments remains challenging. Here we present reverse metabolomics as a discovery strategy, whereby tandem mass spectrometry spectra acquired from newly synthesized compounds are searched for in public metabolomics datasets to uncover phenotypic associations. To demonstrate the concept, we broadly synthesized and explored multiple classes of metabolites in humans, including N-acyl amides, fatty acid esters of hydroxy fatty acids, bile acid esters and conjugated bile acids. Using repository-scale analysis1,2, we discovered that some conjugated bile acids are associated with inflammatory bowel disease (IBD). Validation using four distinct human IBD cohorts showed that cholic acids conjugated to Glu, Ile/Leu, Phe, Thr, Trp or Tyr are increased in Crohn's disease. Several of these compounds and related structures affected pathways associated with IBD, such as interferon-γ production in CD4+ T cells3 and agonism of the pregnane X receptor4. Culture of bacteria belonging to the Bifidobacterium, Clostridium and Enterococcus genera produced these bile amidates. Because searching repositories with tandem mass spectrometry spectra has only recently become possible, this reverse metabolomics approach can now be used as a general strategy to discover other molecules from human and animal ecosystems.